A V Gerasimov

Progress in the generalization of wall-function treatments

Abstract This paper describes progress in developing an analytical representation of the variation of the dynamic variables and temperature across the near-wall sublayer of a turbulent flow. The aim is to enable the effective “resistance” of the viscous sublayer to the transport of heat and momentum to be packaged in the form of a “wall function”, thus enabling CFD predictions of convective heat transfer to be made without incurring the cost of the very fine near-wall grid that would otherwise have to be adopted. While the general idea is not new, the detailed strategy contains many new features, which have led to a scheme capable of accounting for the effects of buoyancy, pressure gradient and of variations in molecular transport properties. The scheme is applied to the problem of forced and mixed convection in a vertical pipe and to the opposed wall jet with encouraging results.

A New Wall-Function Strategy Applied to Mixed Convection in Vertical Annular Passages

The paper summarizes a new analytical formulation of the near-wall region in turbulent flow that has been found to account markedly better for the influence of buoyancy on the flow structure than conventional logarithmic laws. The paper summarizes the key features of this approach and prior applications of the scheme. It then considers the case of vertically downward flow through an annular passage, a configuration often considered in relation to safety studies in nuclear reactors. Four different test-cases are examined for values of the buoyancy parameter, Bo, ranging from 0.22 to 2.89. All show reasonably close agreement with experimental data and with computations using the far more elaborate and costly low-Reynolds-number form of the k-e model.